Hole punch and also a method for the piercing of a workpiece which is present as a foam material and/or as a sandwich material and also a method for the manufacture of the hole punch

ABSTRACT

A hole punch and a method for piercing a workpiece wherein a hole punch includes a sheet metal part and a piercing body attached thereto which carries out the piercing function and which is provided with a thread cylinder or can be provided with a thread cylinder, for example by pressing a threaded pin into a centrally arranged passage of the hole punch, wherein the hole punch can also be formed in one piece as a piercing body with a sheet metal-like flange. Furthermore a method is claimed for the manufacture of the hole punch.

This patent application is a divisional application of, and claimspriority to, U.S. patent application Ser. No. 14/485,881, filed Sep. 15,2014, which claims priority to DE App. No. 102013218548.0, filed Sep.16, 2013, both of which are incorporated herein by reference in theirentireties.

The invention relates to a hole punch and also to a method of piercing aworkpiece which is present as a foam material and/or as a sandwichmaterial, and also to a method for the manufacture of the hole punch.

U.S. Pat. No. 7,160,047 describes amongst other things, novel materialsconsisting of composite material which is defined there as being abrittle or resilient component which consists of a material havinghollow spaces or pores, such as for example plastics, wood, foams,metals which are filled with hollow bodies or plastics or anotherrelatively soft material and are optionally present in the form of asandwich construction, for example in the form of a one-ply or multi-plystructure with, for example, two sheet metal or plastic layers with acore of one of the above-named substances or materials.

The invention is likewise concerned with the processing of workpieces ofthis kind including newer materials which were not available at thattime. In order to more clearly specify the type of materials thefollowing examples can be named which is however not to be considered asa restrictive listing:

a) Foam materials which consist of metal, for example of steel,aluminum, magnesium or titanium or of alloys of these or other metals,with the foam materials having arisen through a foaming process andoptionally being provided with closed or porous skins of the samematerial.

b) Foam materials which consist of metal, for example of steel,aluminum, magnesium or titanium or of alloys of these or other metals,with the foam materials being sintered from powder material withpore-forming substances which volatilize during sintering and alsoprovided here with closed or porous skins of the same material ifrequired.

c) Foam materials in accordance with a) or b) above but with coverlayers of another material or of different materials in order to realizea sandwich construction.

d) Foam materials of plastic, optionally with fiber reinforcement and/orwith upper or lower layers of the same plastic or of another plastichaving smaller or no pores at all in comparison to the core region.

e) Sandwich materials having a core in accordance with d) above and withbonded on or adhesively attached or otherwise attached cover layers ofthe material with the same or different composition.

f) Sandwich material with cover layers of sheet metal materials of thesame or different composition with a bonded on core of another materialsuch as wood, cardboard, card or other materials, optionally inhoneycomb form.

g) Sandwich materials with cover layers of plastic materials with thesame or different composition, optionally with fiber reinforcement andwith a bonded on core of another material such as wood, cardboard, cardor other materials, optionally in honeycomb form.

h) Sandwich materials consisting of a plastic such as ABS (acryl nitrilebutadiene styrene copolymer). Such sandwich materials can be providedwith cover layers of solid ABS and a core of foam ABS, optionally withcolored outer layers, likewise manufactured of ABS, with a materialeither being manufactured in a plurality of layers which are then bondedto one another or can be formed from the outset in one piece. Instead ofmanufacturing such sandwich plates from one material, the individuallayers can also consist of different plastics, optionally with fiber orfabric reinforcement. Plates of such materials can be drawn by deepdrawing to shaped automotive parts such as bonnets, rear doors etc.

ABS is a synthetic terpolymer which consists of three different monomersacryl nitrile, 1,3-butadiene and styrene and belongs to the amorphousthermo plastics. The quantity ratios can thereby vary from 15-35% acrylnitrile, 5-30% butadiene and 40-60% styrene.

By way of example, PLA, polycarbonates, polyester, polyethylene,polypropylene, TPO, TPR/TPE can be considered as further plastics.

Such materials are available from the company ASP-Plastics GmbH, 22145Braak in Germany and from the company Polyone Designed Structures andSolutions LLC, Clayton, Mo., USA and are sold under the designationRoyalex.

i) Panels of massive ABS or comparable plastics such as for example PLA,polycarbonate, polyester, polyethylene, polypropylene, TPO, TPR/TPEwithout a foam core both with and without fiber, fleece or fiberreinforcement.

An important object of the invention is to provide a hole punch and alsoa method for using a hole punch and a method of manufacturing a holepunch which can be rationally manufactured and used on an industrialscale in order to provide workpieces of the above-named type with holesand to provide fastener elements attached in the region of these holes.

In order to satisfy this object, a hole punch is provided in accordancewith the invention for piercing a workpiece, wherein the hole punchconsists of a sheet metal part and a piercing body attached theretowhich carries out the piercing function and which is provided or can beprovided with a thread cylinder.

With this proposal an entirely new path is followed. Through theattachment of the actual piercing body to the sheet metal part a holepunch can be provided at an extremely favorable price for once only use,which can easily be handled via the sheet metal part and in which thesheet metal part which forms a contact surface for the hole punch at theworkpiece restricts the depth to which the piercing body can move intothe workpiece.

Through the provision of a piercing body with a thread cylinder one canadopt a second function directly after the piercing of the workpiece,namely the function of a fastener element. Thus, the sheet metal partcreates the possibility of providing, with a compact piercing body, alarge contact area for the hole punch which is now acting as a fastenerelement, whereby the loading which occurs in operation does not lead toan undesirably high surface pressure.

The use of a fastener element which is attached to or will be attachedto an auxiliary joining part in the form of a sheet metal part isadmittedly known, for similar work materials from the above named U.S.Pat. No. 7,160,047 but there the bore which accommodates the fastenerelement is manufactured otherwise and the component assembly which isdescribed and shown there, consisting of a fastener elements and a sheetmetal part, are not suitable for the use as a hole punch, particularlysince the attachment of the fastener element to the auxiliary joiningpart takes place simultaneously with the attachment of the two parts ina pre-manufactured hole.

In accordance with a particular variant of the invention the hole punchis present prior to use in a strip assembly with a plurality of likehole punches.

A construction of this kind makes it possible to be able to use the holepunch on an industrial scale, because the strip assembly is well suitedfor automatic supply to a piercing head so that for each stroke of thepiercing head the strip assembly is transported further by one holepunch spacing. I.e. the sheet metal strip of the strip assembly servesas a carrier and spacer for the hole punches and is simply cut off inthe piercing head.

In this respect the strip assembly can be present in a straight line orin the form of a coil.

A straight line design, i.e. an embodiment in strip form can be ofadvantage when a restricted number of workpieces is to be processed. Theuse of a strip assembly in the form of a coil has the advantage that alarger number of hole punches can be accommodated in space-saving mannerand can be used in a large scale manufacturing process.

For the hole punch in accordance with the invention the piercing bodycan be connected to the sheet metal part by pressing, by adhesivebonding, by soldering, brazing or welding. Such methods make it possibleto design the manufacture of the hole punches in accordance with theinvention in a rational manner, since they can be manufactured as a rulefrom right cylindrical piercing bodies and a sheet metal strip, with thesheet metal strip serving as a transport device for the piercing bodiesand being subsequently divided up to form the individual hole punchesconsisting of a sheet metal part and a piercing body.

The piercing body is preferably secured to the sheet metal part in amanner secure against rotation. In this way, the area or the shaping ofthe sheet metal part can be exploited for the attachment of the holepunch to the workpiece in a manner secure against rotation. This is ofadvantage when the thread cylinder of the hole punch is subsequentlyused for the attachment of a further component to the workpiece, eitherby use of a bolt which is screwed into a female thread cylinder or bythe use of a nut which is screwed onto a male thread provided at thepiercing body.

The sheet metal part and/or the piercing body can be provided with meansproviding security against rotation.

For this, a plurality of possibilities is available. The means providingsecurity against rotation can be formed by features of shape of thesheet metal part such as bent down corners of the sheet metal part, theshape or contour of the sheet metal part, the shaping of the side edgesof the sheet metal part and/or raised features, recesses or holes of thesheet metal part.

The means providing security against rotation can moreover be formed byfeatures of shape of the piercing bodies, such as longitudinal ribs atthe envelope surface of the piercing body or a grooved or ribbed orpolygonal or non-circular outer shape of the piercing body. Such shapescan also be straightforwardly used with a piercing die having a simpleright cylindrical bore, because the piercing body is as a rule selectedwith a length to the sheet metal part which is significantly shorterthan the thickness of the workpiece and thus no danger exists that theshape of the piercing body which is used just once leads to damage tothe die button, which is used many times.

As an alternative to the above indicated possibilities the meansproviding security against rotation could also be formed by an adhesive.Suitable adhesives are well known in the field of fastener elements andfrequently consist of a material which first hardens under theapplication of pressure. The components of the adhesive can beaccommodated in small capsules and can first mix and react when pressureis exerted.

It is particularly favorable when the piercing body is formed by afastener element which is either provided with an internal thread orwith a shaft part having an external thread which projects away from thepiercing body remote from the sheet metal part or is itself used tocarry out the piercing function.

Such fastener elements are excellently suited to be secured by a tubularrivet section or by suitable undercuts to a sheet metal part by rivetingand/or by pressing in, i.e. they can be present as a rivet element or asa piercing and rivetingt element or as a press-in element.

Furthermore, so-called weld elements can be used as piercing bodies,i.e. nut-like or bolt-like elements which are provided with weldingpoints which enable them to be welded to a sheet metal part or to asheet metal strip.

The invention furthermore includes a method for the attachment of afastener element to a workpiece which is at least partly formed of foammaterial such as plastic, aluminum, magnesium or steel and is optionallypresent in a composite with one or more further components or materialsand/or which is formed from sandwich materials of all kinds and the mostdiverse compositions, for example, such as those having a core of foammaterial such as cardboard, card or wood, wherein a hole punch,consisting of a sheet metal part and a piercing body secured thereto, isdriven with the piercing body to the fore against a first side of theworkpiece while the workpiece is supported at its oppositely disposedside by a piercing die the hole of which is selected suitably for thecross-sectional shape of the piercing body and hereby a piercing slug ofthe material of the workpiece is cut out, the sheet metal part, isbrought into contact against the said first side and is optionallypressed into the latter in order to bring features providing securityagainst rotation provided at the sheet metal part and/or at the piercedbody into engagement with the workpiece.

In this method, the hole punch is only used once in order to pierce ahole through the workpiece and remains in the workpiece in order toserve as a fastener element.

The above recited method can also be automated in a favorable manner ifa plurality of hole punches are supplied in a strip assembly to apiercing head which is operated in strokes and which for each strokeseparates one hole punch from the strip assembly and pierces theworkpiece with it.

When the strip assembly consists of a sheet metal strip and a pluralityof piercing bodies attached thereto, the sheet metal strip can besubdivided in the piercing head into individual sheet metal sectionswhich are each secured to a piercing body.

The method can also be further developed so that the piercing headsimultaneously serves, on separating the hole punch from the stripassembly, for shaping of the sheet metal part, for example, to generatefeatures of shape which form a security against rotation with theworkpiece.

The method of the invention is preferably carried out in a press.

A procedure of this kind is suitable for mass production of components.The use of such piercing heads is however not restricted to the use in apress. Instead of this, a piercing head could be carried or actuated bya robot which moves the piercing head in the direction towards the diebutton or vice versa. Force-actuated tongs can also be sued.

The press can also be equipped with a progressive tool which, for eachstroke of the press, carries out a plurality of operations in differentstations of the progressive tool, with a piercing head being used ineach station or in a plurality of stations of the progressive tool.

The method can also be so further developed, that the piercing slug isremoved in the same stroke of the piercing head or in a second stroke ofthe piercing head by means of a further plunger which is moved through abore of the hole punch, i.e. of the sheet metal part and the piercingbody.

The invention also includes a method for the manufacture of a stripassembly consisting of a plurality of like hole punches, wherein a stripof sheet metal drawn off from a carrier is supplied to a tool whichsecures the piercing bodies at regular intervals along a longitudinalaxis of the sheet metal strip to the latter.

This method can be particularly favorably carried out when the sheetmetal strip having a plurality of hole punches is cut into length orrolled up into a coil.

The manufacturing process for the sheet metal strip having a pluralityof piercing bodies can be effected in a progressive tool operating instrokes, which carries out a plurality of operations for each stroke.

This process also makes it possible to carry out shape-giving work atthe sheet metal strip, for example the punching out of holes in thesheet metal strip which serve for security against rotation at theworkpiece and/or of the manufacture of slits and/or notches in the sheetmetal strip which then serve for the later transport in the piercinghead or for the later subdivision in the piercing head. Furthermore, itcan be favorable to ensure an improved rolling up behavior by shaping ofthe sheet metal strip. For example, U-shaped bars or folds can beproduced between the sheet metal parts which can be separated from oneanother which ensure a stable coil.

The invention will subsequently be explained in more detail withreference to embodiments and to the drawings in which are shown:

FIG. 1 a perspective representation of a press for the manufacture of astrip assembly of the hole punches in accordance with the invention,

FIG. 2 a perspective representation of a strip assembly manufactured inFIG. 1 and of a hole punch in accordance with the invention which hasbeen separated from it,

FIGS. 3A-3E a hole punch in accordance with the invention in aperspective view from below (FIG. 3A), in a perspective view from above(FIG. 3B), in a plan view on the lower side (FIG. 3C), in partlysectioned view (FIG. 3B) in accordance with the arrow 3D in FIG. 3B andin a partly sectioned view (FIG. 3E) in accordance with the section line3E in FIG. 3C and

FIGS. 4A-4C three phases of the use of a hole punch in accordance withthe invention.

Referring to FIG. 1 it is shown there how a sheet metal strip 12 drawnfrom a carrier 10 is used in a tool 14 of a press 16, shown here as afour column press, for the manufacture of a strip assembly 20 consistingof a plurality of like hole punches 18. For this purpose, a plurality ofpiercing bodies 22 which are first shown on their own in FIG. 2A aresupplied to the tool 14 and are secured at regular spacings along thelongitudinal axis A of the sheet metal strip 12 to the latter. This cantake place using corresponding setting heads (not shown) in the tool 14.

The press 16 or the tool 14 which is contained therein can be sodesigned that for each stroke of the press a plurality of piercingbodies 22 are secured to the sheet metal strip 12 and the sheet metalstrip 12 is then transported further as a whole by the effective widthof the tool 14. Alternatively, a progressive tool can be used for thispurpose (as shown here), which not only attaches one or a plurality ofpiercing bodies 22 to the sheet metal strip 12 for each stroke of thepress 16 but rather itself also carries out certain work on the sheetmetal strip 12. Such work can include a pre-piercing and/or a conicaldeformation of the sheet metal strip 12 around the pierced hole, whichis for example the case for the attachment of piercing bodies inaccordance with the so-called clamping hole riveting process.

In other words, the tool 14 can be a progressive tool operating instrokes which carries out a plurality of operations for each stroke. Thetransport length of the sheet metal strip 12 between each strokecorresponds to an integral multiple of the spacing of the individualhole punches 18, with the number depending on the design of theprogressive tool.

The sheet metal strip 12 manufactured in this way with the apparatus ofFIG. 1 and having a plurality of hole punches 18 can then be cut-up intolengths after or in the press 16 or, as shown in FIG. 1, can be rolledup into a coil 24.

The press 16 of FIG. 1 is simply one example for the possible attachmentof the piercing bodies 22 to a sheet metal strip 12. When the piercingbodies are present in the form of weld elements then they can be weldedonto the sheet metal strip individually or in a multiple arrangement ina suitable apparatus.

When using the strip assembly 20 of hole punches 18, the strip assembly20 is supplied to a piercing head (not shown) irrespective of whetherthe strip assembly is present in individual lengths or in the form of acoil. For each working stroke of the piercing head the piercing headseparates one hole punch 18 from the strip assembly 20, as schematicallyshown at the left hand side of FIG. 2. One can see from FIG. 2, that theindividual hole punches 18 are secured in the strip assembly 20 only viacentrally arranged connection webs 26, with the webs 26 being bounded onboth sides by approximately U-shaped cuts 28 of the sheet metal strip 12from the longitudinal side 30, 32 of the sheet metal strip 12 and inthis example are also provided with a notch 34. Furthermore, one can seethat the corners 36 of the hole punch 18 are bend downwardly in order toform claws 38 which engage into the material of workpiece 40 in ordergenerate a high quality security against rotation.

As can likewise be seen from FIG. 2 the sheet metal part 44 has corners36 bent in the direction of the nut body 23. These corners 36 serve assecurity against rotation. The transmission of large forces to therelatively weak foam material is also ensured via the large contact areaat the sheet metal part.

With reference to the FIGS. 3A to 3E the piercing bodies in the form ofan RSN element can be seen in the riveted form with the sheet metalpart. The RSN element has a cylindrical body part 23 which is circularin plan view with a small radius 54 at the free end face 56, this radius54 should be as small as possible in order to improve the piercingcharacteristics of the free end face 56. At the side remote from thefree end face the RSN element has a rivet section 52 which, in thestarting state, i.e. prior to the fastening of the element 42 to thesheet metal part 44 is tubular but has here been reshaped into a rivetbead 58. Around the rivet section 52 there is a sheet metal contactsurface 60, with features providing security against rotation (notshown) being provided at the sheet metal contact surface 60, or in theregion of the transition from the rivet section 52 into the sheet metalcontact surface 60. These features providing security against rotationcan for example take the form of ribs which are however not visiblehere. These features providing security against rotation bring about asecurity of rotation at the sheet metal part 44, whereby the piercingbody 22 is secured to the sheet metal part 44 in a manner securingagainst rotation. As the sheet metal part 44 is firmly clawed to theworkpiece, in this example by the downwardly bent corners 36, thepiercing body 22 is thus secured to the workpiece 62 (FIG. 4) via thesheet metal part 44 in a manner securing against rotation.

The piercing body 22 is provided here with an internal thread 46 so thata further component (not shown) can later be secured to the workpiece 62and indeed by a threaded bolt which is screwed into the thread 46 fromthe side remote from the sheet metal part 44 so that the furthercomponent is clamped between the head of the bolt and the side of theworkpiece remote from the sheet metal part. That is to say iseffectively clamped to the workpiece 62 by a clamping load exertedbetween the head of the bolt and the sheet metal part 44. A securityagainst rotation of the sheet metal part relative to the workpiece 62cannot only be achieved by corners 36 of the sheet metal part 44 butrather, alternatively or in addition to this, by the shaping of thecontour of the sheet metal part 44, the shaping of the side edges of thesheet metal part 44 and/or raised portions, recesses or holes of thesheet metal part. Such features providing security against rotation canbe considered, because the punching of the piercing body into theworkpiece is also associated with a certain pressing of the sheet metalpart into the corresponding surface of the workpiece, so that anadequate material engagement takes place in order to ensure the securityagainst rotation.

It is also conceivable to provide means providing security againstrotation by features of shape (not shown) of the piercing body 22, suchas longitudinal ribs at the envelope surface of the piercing body, agrooved or ribbed or polygonal or non-circular outer form of thepiercing body.

The method for the attachment of the fastener element 42 to a workpiecewhich consists at least in part of a foam material such as plastic,aluminum, magnesium and/or steel and which is optionally present in acomposite with one or more further components or materials and/or whichis formed from sandwich materials of all kinds and diverse compositions,for example also those with a core of foam material, cardboard, card, orwood will now be described with reference to FIGS. 4A to 4C.

In accordance with FIG. 4A a hole punch 18 in accordance with theinvention and in accordance with FIGS. 2A to 2E is driven with thepiercing body 22 to the fore against a first side 64 of the workpiece 62in the arrow direction B while the workpiece in accordance with FIG. 4Bis supported at its oppositely disposed side by a piercing die 50 thehole 66 of which is selected to suit the cross-sectional shape of thepiercing body. In this way a piercing slug 48 is generated from thematerial of the workpiece 62 which, in FIG. 4B, has not yet been fullypressed out of the workpiece 62. The sheet metal part 44 is so firmlypressed against the workpiece 62 that the bent down corners 36 penetrateinto the upper cover layer 68 of the workpiece 62 and there serve forthe security against rotation. I.e. the sheet metal part 44 is broughtinto engagement at the said first side 64 and is optionally pressed intothe latter and the means providing security against rotation provided atthe sheet metal part 44 and/or at the piercing body 22 are brought intoengagement with the workpiece 62.

One notes, that the axial height H of the piercing body 22, which ismeasured below the contact surface 70 of the sheet metal part 44 fromthe sheet metal part 44 to the free end of the piercing body 22, issmaller than the total thickness D of the workpiece. Depending on howthis height/thickness ratio is selected and depending on which specificmaterial is used for the workpiece it can transpire that the piercingslug 48 already fully drops out of the workpiece in the stage of FIG.4B, as shown in FIG. 4C. Should this not transpire, because the saidheight/thickness ratio of the material does not permit this, then thepiercing slug 48 can be pressed out by means of a follow-up plungerwhich is moved through the threaded bore of the piercing body 22. Thefollow-up hole punch 18 can be used in the same stroke of the insertionapparatus when a spring-loaded press part is used in the (not shown)piercing head in order to actuate the hole punch 18 and to move theplunger (not shown) thus removing the slug in the same stroke of theinsertion device including the piercing head.

Alternatively to this, a plunger can be used to remove the piercing slug48 in a second stroke of the tool, which also takes place here throughthe central passage 72 of the hole punch 18 and the piercing body 22.The finished workpiece is then shown in FIG. 4C.

The setting head of the insertion device can be built up similarly to apiercing head which is used in a press in order to transport “nuts onwire” and to punch them into a workpiece. Nuts on wire relates torectangular elements which are pressed onto two parallel wires and foreach stroke of the press are cut through in order to punch individualrectangular elements into the workpiece. However, the piercing head doesnecessarily have to be used in a press, but rather it can also becarried by a robot or by force-actuated tongs (both not shown) whichmove the piercing head in the direction towards a die button.

Although it is preferred, in accordance with the invention, to secureindividual piercing bodies to a sheet metal strip and to subsequentlysubdivide this, it should also be mentioned that a hole punch can alsobe formed in one piece as a piercing body with a sheet metal-likeflange. Such hole punches can, for example, be manufactured in a coldheading process.

In other words, in the specific embodiment of FIG. 1, rivet elements 42of the present applicant in the form of an RSN element are riveted aspiercing bodies 22 into a sheet metal strip 12, with the individual holepunches 18, which each consist of a sheet metal part 44 and a piercingbody 22 carrying out the piercing function secured to it, which is orcan be provided with a thread cylinder 46. After the riveting in processthe hole punches 18 are not present individually but rather are wound upas strips into a coil 24. This coil then serves as a belt for beingdrawn into the piercing head (not shown) during insertion of theelements into the foam material.

For each stroke of this piercing head the element is accordinglyseparated. The punching in process takes place via the nut element 42 asa piercing body.

Depending on the thickness ratio of the material and the nut, the slug48 (FIG. 4) is pressed completely out or remains sticking in the diebutton 50 (FIG. 4) or must be expelled by a second stroke by means of aplunger (not shown) which is moved through the thread 46 of the nut 42or is expelled in the same stroke by means of a follow-up plunger (notshown).

An RSN element is only one example for an existing nut element which canbe used for the purpose of the invention. Almost any known rivet nutelement can be considered of which the body part 23 has an internalthread 46 and a shape at the side remote from the rivet section 52 whichis suitable as a piercing body. For example, a modified RND element ofthe present applicants could be used if the body part is madecylindrical and executed with a smaller cross-section or, in otherwords, if the V-shaped groove of an RND nut, which surrounds the rivetsection at the sheet metal contact surface, were to be integrated in anRSN element. In this way the rivet bead by means of which the nutelement is secured to the sheet metal part or to the sheet metal stripcan be made shallower or flatter because it can be hidden in theV-shaped recess which arises when the sheet metal material is receivedin the V-shaped groove.

Furthermore, nut elements can be used which are present as press inelements, for example an RSU element of the present applicants. RSUelements and their processing can be seen from EP-A-759510.

Bolt elements can also be used which are known as rivet elements or aspress in elementsm providing the head part of the bolt is designed as apiercing body. For example, bolt elements of this kind are SBF rivetbolts of the present applicants. The SBF element is for exampledescribed in U.S. Pat. No. 4,555,838 and in U.S. Pat. No. 4,459,073. TheSBF element and the method for the attachment of the element aremoreover set forth in the U.S. Pat. No. 4,543,701 and in the U.S. Pat.No. 4,727,646. An improved version of the SBF bolt can be found inEP-B-1430229.

The use of a bolt element is admittedly associated with the disadvantagethat the workpiece must first be indented or indeed pierced by the shaftpart of the bolt element before the head part or the side of the flangeremote from the rivet section can be used as a piercing tool. This is,however, entirely possible with some materials. With materials in whichthe indenting or piercing with the shaft part of the bolt element cannotbe considered, a hollow element can be used as a piercing body which isriveted, welded or secured otherwise to the sheet metal part, and athreaded bolt having suitable features providing security againstrotation (for example knurled ribs and a countersunk head (similar to apressed in wheel bolt) can be pressed into the hollow element after thepiercing of the workpiece. With an arrangement of this kind the threadedbolt can also serve to punch out any not yet removed piercing slug fromthe workpiece.

As an example of the material of the sheet metal part all sheet metalsteels in a deep drawing quality or somewhat harder and sheet metalparts of aluminum alloys can be named. As an example for piercing bodiesall materials can be named as a material for the piercing rivets in allembodiments which achieve the strength values of class 8 in accordancewith the ISO standard to a cold deformation, for example a 35132 alloyin accordance with DIN 1654. Aluminum alloys, in particular those ofhigher strength, for example AlMg5 can be used for the piercing rivets.Fastener elements of higher strength magnesium alloys such as forexample AM50 can also be considered.

REFERENCE NUMERAL LIST

-   10 carrier-   12 sheet metal strip-   14 tool-   16 press-   18 hole punch-   20 strip assembly-   22 piercing body-   23 body part-   24 coil-   26 connection webs-   28 U-shaped cut-   30 longitudinal side-   32 longitudinal side-   34 notch-   36 corners-   38 claws-   40 workpiece-   42 fastener element-   44 sheet metal part-   46 thread-   48 piercing slug-   50 die button-   52 rivet section-   54 radius-   56 end face-   58 rivet bead-   60 sheet metal contact surface-   62 workpiece-   64 upper side-   66 hole-   68 cover layer-   70 contact surface-   72 passage-   A longitudinal axis-   B arrow direction-   H axial height-   D thickness of workpiece

The invention claimed is:
 1. A method for manufacturing a compositestrip assembly of a plurality of like hole punches comprising: supplyinga plurality of piercing bodies to a tool of a press, drawing a sheetmetal strip off from a carrier and supplying it to the tool, andpermanently securing the piercing bodies to separately formed sheetmetal parts of the sheet metal strip at regular spacings along alongitudinal axis of the sheet metal strip.
 2. A method in accordancewith claim 1, wherein the sheet metal strip having plural hole punchesis one of cut into lengths including a plurality of the sheet metalparts and rolled up into a coil.
 3. A method in accordance with claim 1,wherein the tool is a progressive tool operating in strokes whichcarries out a plurality of operations for each stroke.
 4. A method inaccordance with claim 3, wherein the plurality of operations includeattachment of a plurality of piercing bodies for each stroke of theprogressive tool.
 5. A method in accordance with claim 4, in whichshaping work is simultaneously carried out at the sheet metal strip inthe progressive tool.
 6. A method in accordance with claim 5, furtherincluding forming claws on the sheet metal parts configured to securethe sheet metal parts against rotation relative to a workpiece via theshaping work.
 7. A method in accordance with claim 1, further includingsecuring the piercing bodies against rotation relative to sheet metalparts.